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Percutaneous treatment of aortic valve stenosis

Cleveland Clinic Journal of Medicine. 2008 November;75(11):805-812
November 1, 2008|Cleveland Clinic Journal of Medicine
Inder M. Singh, MD, MS;Mehdi H. Shishehbor, DO, MPH;Ryan D. Christofferson, MD;E. Murat Tuzcu, MD;Samir R. Kapadia, MD
Author and Disclosure Information

Inder M. Singh, MD, MS
Department of Cardiovascular Medicine, Cleveland Clinic

Mehdi H. Shishehbor, DO, MPH
Department of Cardiovascular Medicine, Cleveland Clinic

Ryan D. Christofferson, MD
Department of Cardiovascular Medicine, Cleveland Clinic

E. Murat Tuzcu, MD
Department of Cardiovascular Medicine, Cleveland Clinic

Samir R. Kapadia, MD
Department of Cardiovascular Medicine, Cleveland Clinic

Address: Samir Kapadia, MD, Department of Cardiovascular Medicine, F25, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195; e-mail kapadis@ccf.org

Dr. Shishehbor’s work is supported in part by the National Institutes of Health, National Institute of Child Health and Human Development, Multidisciplinary Clinical Research Career Development Programs Grant K12 HD049091.

ABSTRACTAortic valve replacement via open heart surgery, although still the standard treatment for severe symptomatic aortic valve stenosis, is not an option for many patients with severe symptoms, and these patients are often left with suboptimal strategies such as medical management or balloon valvuloplasty. But over the last 5 years improvements in percutaneous approaches to implantation of prosthetic aortic valves have made it a potential therapeutic option for these patients. Technical and device issues are being refined, and percutaneous aortic valve replacement is showing promise in ongoing clinical trials.

KEY POINTS

  • Aortic stenosis is the most common valvular condition, affecting 3% of the general population; its incidence and prevalence are increasing as the population ages.
  • Many patients with severe aortic valve stenosis are considered too high-risk for standard surgical valve replacement but may be candidates for percutaneous valve replacement.
  • Of the approaches now undergoing refinement, the most promising is retrograde (ie, femoral arterial) placement of the Edwards SAPIEN valve or the CoreValve.
  • The technology is still evolving, and the learning curve is substantial, yet cautious enthusiasm about percutaneous aortic valve replacement is justified.

EXPERIENCE WITH THE COREVALVE SYSTEM

The CoreValve ReValving system is based on retrograde implantation of the CoreValve prosthesis—a self-expanding aortic valve prosthesis composed of three bovine pericardial leaflets mounted and sutured within a self-expanding 50-mm-long nitinol stent (Table 1).28–30 The inner diameter is 21 to 22 mm.28–30 This prosthesis has three distinct structural segments.28–30 The bottom portion exerts a high radial force that expands and pushes aside the calcified leaflets and avoids recoil; the central portion carries the valve, and it tapers to avoid the coronary artery ostia; and the upper portion flares to fixate and stabilize the deployed aortic valve prosthesis in the ascending aorta, thus preventing migration or embolization of the device.28–30 The main difference between the CoreValve and the Cribier-Edwards valve is that the Core-Valve is self-expanding, which theoretically permits it to conform to different aortic sizes and to anchor well in the aortic annulus.28–30 This feature allows the CoreValve to be used in patients with severe aortic insufficiency and other noncalcific aortic valvular conditions. The CoreValve has not yet been deployed via antegrade or transapical technique.

The first-generation CoreValve prosthesis was first implanted in a human recipient in 2005.29 Since then, improvements have been made, leading to the development of second- and third-generation devices. A pilot study of implantation of the first-generation CoreValve28 via the retrograde approach in elderly patients with poor functional class and severe aortic stenosis had a short-term procedural success rate of 84% (21 of 25 patients), with a significant reduction in the mean aortic valve gradient and improved functional class at 30-day follow-up.28 At 30 days, 17 (94%) of 18 patients had no or only mild aortic regurgitation.28 Procedural limitations and complications were similar to those with the Cribier-Edwards valve.

In a study of second- and third-generation devices (50 patients received a second-generation device, and 36 received a third-generation device),30 again in elderly patients with poor functional class and severe aortic stenosis, the short-term success rate of the device was 88% (76 of 86) in each group. After the procedure, the mean aortic valve gradient decreased significantly and functional class improved significantly.30 Immediate after implantation, no patient had more than moderate aortic regurgitation, and in 51 patients (66%) the aortic regurgitation remained unchanged or improved after CoreValve implantation.30 These results were maintained at 30-day follow-up.

CoreValve was approved in May 2007 for clinical use in Europe.36 Of note, CoreValve has also been used to treat severe aortic regurgitation of a degenerated bioprosthetic aortic valve in an 80-year-old man with multiple comorbidities.37

EXPERIENCE WITH THE EDWARDS SAPIEN VALVE

The Edwards SAPIEN valve is a modification of the initial Cribier-Edwards valve and is the latest percutaneous aortic valve prosthesis to enter clinical trials (Table 1). It is a trileaflet balloon-expandable stainless steel valve made from bovine pericardial tissue, available in two sizes (23 mm and 26 mm). In September 2007, it was approved for use in Europe with the RetroFlex transfemoral delivery system. The Ascendra transapical delivery system for the Edward SAPIEN valve has received approval in Europe.

The multicenter Placement of Aortic Transcatheter Valves (PARTNER) trial in North America is continuing to enroll patients, with enrollment projected to be complete by the end of 2008. The aim of this prospective randomized clinical trial is to enroll 1,040 patients in two separate treatment arms. The surgical arm of the trial is comparing the Edwards SAPIEN valve with standard surgical aortic valve replacement, with the objective of demonstrating non-inferiority. The medical management arm of the trial is comparing percutaneous valve replacement against medical therapy or balloon valvuloplasty in patients considered too high-risk for conventional surgical valve replacement.

The primary end point in both arms is death at 1 year; secondary end points focus on long-term (1-year) composite cardiovascular events, valve performance, and quality-of-life indicators. Preliminary data on the first 100 patients (74 via the transfemoral [ie, retrograde] and 26 via the transapical approach) who underwent percutaneous Edwards SAPIEN valve implantation for compassionate use showed device durability and symptom relief at up to 2 years.38 Overall procedural success was 91%, but, as with other trials, there was a steep learning curve, so that excluding the first 25 patients increased the procedural success rate to 96%.38 Aortic valve size and hemodynamics, left ventricular systolic function, mitral regurgitation, and functional class were all significantly improved. Mild aortic regurgitation was common, but none of the patients had severe aortic regurgitation. Importantly, the 15% 30-day death rate was significantly lower than the expected rate of 33%. The 6-month survival rate was 78%, but the 2-year rate was 60% in this high-risk elderly cohort.

Walther et al39 recently reported outcomes on their first 50 patients who underwent transapical implantation of the Edwards SAPIEN valve. The operators were able to implant the prosthesis in all 50 patients, but 3 required early conversion to open surgery with sternotomy. The overall survival at 30 days was 92%, but in the last 25 patients the 30-day survival rate was 96%, with a 1-year survival rate of 80%.

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